Molecular responses of phytoplankton to iron limitation

Molecular responses of phytoplankton to iron limitation

著者 モハメド マムヌール ラハマン

著者別表示 Md Mamunur Rahman journal or

publication title

博士論文要旨Abstractおよび要約Outline 学位授与番号 13301甲第3955号

学位名 博士（学術）

学位授与年月日 2013‑09‑26

URL http://hdl.handle.net/2297/37353

Creative Commons : 表示 ‑ 非営利 ‑ 改変禁止 http://creativecommons.org/licenses/by‑nc‑nd/3.0/deed.ja

様式 ４．

学

Molecular responses of phytoplankton to iron limitation

（和訳） 植物プランクトンの鉄制限に対する分子応答 物質科学 専攻 物質情報解析 講座

MD. MAMUNUR RAHMAN

主任指導教員氏名 長谷川 浩

The present study showed that marine phytoplankton employ several strategies to compensate Fe stress whether it is due to low total Fe or low Fe availability. The present study reveals that marine phytoplankton produce different proteins under low total Fe and ligand-induced Fe-limited conditions. Protein expression under different Fe conditions also varied within phytoplankton species (Prymnesium parvum, Skeletonema marinoi-dohrnii complex and Pleurochrysis roscoffensis). This study also reveals that several proteins are differentially expressed in marine phytoplankton P. parvum in response to different exposure levels of nitrate, phosphate and iron. The expression levels of an 83 kDa protein in P. parvum can be used as biomarker of N-status, while a 121 kDa protein can be used as a biomarker of P-deplete condition in aquatic systems. In addition, two protein can be used as biomarker of Fe-status (deplete or replete conditions) in aquatic systems. Under Fe-limited condition, marine phytoplankton P. parvum alters some of its cellular biochemical processes by up-regulating proteins that are assumed to be involved in Fe uptake, photorespiration, and reduction of oxidative stress in the cells. Prymnesium parvum may increase Fe uptake efficiency by increasing Fe acquisition sites (mediated by ABC transporters) when they are grown under Fe-limited condition. Under Fe-limited condition, P. parvum may also increase photorespiration which needs high metabolic energy. The phytoplankton may satisfy the demand of high metabolic energy by increasing ATP synthase in chloroplast. Oxidative stress in phytoplankton is thought to be induced by Fe-limitation. P. parvum is assumed to up-regulate oxidative stress response proteins MnSOD and STK to minimize the oxidative stresses by inactivating the access electrons in the cells. It was also found that carbohydrate degradation and glycolytic activity was increased under Fe-limited conditions. Marine phytoplankton P. parvum also alters its cellular biochemical processes by up-regulating several proteins involved in photosynthesis.

The phytoplankton also increased biosynthesis of PSII component proteins under

Fe-limited conditions.